I have been reading Lingua Latina Pars I for almost two months now and have really enjoyed and learned much from it. And given the long wait I had on Amazon for it, I was going to order Roma Aeterna ahead of time, before I finish it. I was just wondering if there are any other LL texts, or Latin texts in general I should order with it.

The only supplement I have besides the core books is Caesar's De Bello Gallico, which I recommend. We used it the first semester of my second year course, and I was coming to it straight from Wheelock's. In retrospect, coming from LL vol. 1, it would be easy and enjoyable. All the grammar/vocab is aided in the margins as you're familiar with, and I think you'll find the text straightforward and the content interesting. The text is unedited and focuses on interesting passages. The tougher grammar is in the occasional, long, indirect discourse paragraphs, but Orberg lays it all out for you.
http://www.vivariumnovum.it/_pdf/_qualc ... allico.pdf

I haven't used it, but Orberg's edition of Plautus looks entertaining and is geared for those who have finished Familia Romana: